The question as to why I choose this topic? I decided to do a research paper on structural failure because it is an area that I have been working in for most of my adult life. It’s an area that I like to study and because of that, I am a sought after Marine in this field at work. In a squadron, I am considered a resident expert and thrive to constantly be on the top of my game.
History of Aircraft Structures
Structural failures are an interesting topic because without a sound structure, flight wouldn’t be possible and where would we be today? When breaking down the aspects of heavier-than-air flight, aerodynamic lift has to be generated and this is usually accomplished by wind rushing over a wing. To get us where we are today, early inventors experimented with such contraptions as kites, gliders and airplanes. Without the wind, kites and gliders are rendered useless since their main sustainment of lift is wind. Airplanes on the other hand utilize a means of propulsion to propel them through the air causing wind to generate lift as it rushes over the wings (Bell, 2014).
The history of the general construction of an aircraft and associated components throughout history has been comprised of various materials. Aviation pioneers had to utilize wood as the main component in making their aircraft as they were testing their theories. Heavier-than-air flight was achieved by the Wright Brothers in 1903, when their powered aircraft carried a man aloft and it was only comprised of wood truss structure and thin fabric covered wings. Over the next few years, engine development greatly advanced with more powerful and reliable models that in 1910, Hugo Junkers; a German inventor developed a metal constructed aircraft. This aircraft, called the J-1was constructed with metal trusses and the skin wrapped metal as well. The combination of both a powerful engines and metal construction eliminated the need of stacked wings and a monoplane was developed without the need of wires and wing braces (Federal Aviation Administration, 2012).
By 1926, semi monocoque construction took hold, resulting in stronger and bigger aircraft. The principle behind this construction is instead of having a skeleton structure that the skin was attached and stretched over, only partial structures would be utilized with reinforcing bulkheads and much of the load would be carried with the skin. These reinforced bulkheads would help carry the associated stresses of flight. Using this structure allowed the aircraft to remain light, with powerful engine that eventually lead to the development of plastics (Flannigan, 2010).
Now plastics are not strong enough to support the structure of an entire aircraft that researchers found out but could be used for smaller components and hence, glass fibers was developed to be better known as fiberglass. Owens Corning, in 1935 developed the first fiberglass that when combined with a product such as a plastic polymer could create a lightweight and strong structure. This development is still used today in an industry known as FRP, Fiber Reinforced Polymers (Jones, 2013).
World War II created supply and demand for military aircraft to be lightweight and through further development, Radomes were developed. Radomes are utilized to shelter major electronic components as the structure of the radome is fiberglass and has a transparent quality for radio frequencies. With this breakthrough, the composites industry took a giant leap from scientific research working in laboratories with models and scientific studies, to being full scale production. In 1946 the first composite boat hull was develop and now both the marine and aviation industries benefited from their further research. In the industry today, composites lead the way with the development of carbon fiber, Aramid, Kevlar and graphite composites (Federal Aviation Administration, 2012).
Structural failure contributors Structural failures have been long associated with the individual metal components or complete structures of an aircraft. An aircraft when assembled already has weakness incorporated into them that the manufacture might not associate with. These components will begin to weaken at these points when imposed stresses are acted upon each part during operation. The following are stress prone areas that have the most concentration of structural failures (Bell, 2014):
1. Manufacturer design flaws or machining errors that leave the small imperfections, e.g. holes, burrs, voids, notches and in the forming processes, tight fillet radii.
2. Metal extruded parts might have the same associated flaws during their manufacturer processes that could leave inclusions, pitting, voids etc.
3. From production to service life, corrosion is ever so prevalent that companies pay workers to combat the ongoing spreading of corrosion. Different types of corrosion that cause structural failures are: Uniform attack corrosion, localized corrosion (pitting, crevice, and filiform corrosion), galvanic corrosion, environmental cracking, flow-assisted corrosion, and fretting corrosion.
4. In-flight
What does all that mean?
• Uniform Attack Corrosion: Most common associated form of corrosion that occurs when a chemical reaction to the entire surface of the metal component occurs. The entire exposed surface will corrode to the point of failure. This form does cause the most corrosion of metal components, but it easily overcome since it predictable, preventable and manageable.
• Localized Corrosion: Targets specific metal components in one of three types: pitting, crevice and filiform corrosion.
• Pitting: Pitting is formed by cavities or small holes in the metal that create a galvanic environment making it hard to detect.
• Crevice Corrosion: Just the same as pitting corrosion but with the inhibitor of mirco-environment sitting stagnant. This micro-environment can be found where gaskets, clamps and washers are utilized.
• Filiform Corrosion: Water is the culprit with filiform corrosion. It’s caused when painted or plated surfaces begin to erode and water intrudes behind them.
• Galvanic Corrosion: When two dissimilar metals are mated together with each other to cause a corrosive electrolyte. Of the two metals, each takes a separate roll of anodes and cathodes. To create a galvanic corrosion environment, three conditions must be met:
1. Two dissimilar, electrochemically metals must be present.
2. Metals must be electrically contact as whatever point.
3. An electrolyte must be present and exposed to the metals.
• Environmental Cracking: Environmental conditions against the metals.
• Flow-Assisted Corrosion: Erosion from flight or being susceptible to the environment when rain and wind wear down the outer layers, exposing the metals.
• Fretting Corrosion: Constant repeated wear from the aircraft's weight or vibration from flight. When looking at all of this as a big picture, an investigator during a mishap investigation would be using pretty much any air detective tip to help solve and determine what caused the mishap in the first place.
When a structural mishap occurs, investigators will be looking at all aspects of every piece left of the aircraft. If corrosion was evident, one might suspect the overall maintenance of the aircraft could have been in jeopardy. The SHELL concept could be a great detective tip to utilize because the investigator could compare the Liveware (human) and the factors associated with the aircraft. The accident in general could have been associated with the maintenance malpractice of the maintainers concluding the interface of the pilots not knowing that their aircraft was susceptible to structural failure.
References
Bell, T. (2014, January 14). Types of corrosion: What are the different types of corrosion?. Retrieved
from http://metals.about.com/od/metallurgy/a/Types-Of-Corrosion.htm
Federal Aviation Administration (2012). Aviation maintenance technician handbook. (Vol. 1, pp.
21-75). Oklahoma City, OK: United States Department of Transportation, Federal Aviation
Administration, Airman Testing Standards Branch. Retrieved from http://www.faa.gov
/regulations_policies/handbooks_manuals/aircraft/amt_airframe_handbook/media
/amt_airframe_vol1.pdf
Flannigan, P. (2010, January 19). Semi monocoque, mono-what?. Retrieved from
http://www.aviationchatter.com/2010/01/semi-monocoque-mono-what/
Jones, T. (2013, August 10). Owens corning records , 1938 - present . Retrieved from
http://www.utoledo.edu/library/canaday/findingaids1/MSS-222.pdf
History of Aircraft Structures
Structural failures are an interesting topic because without a sound structure, flight wouldn’t be possible and where would we be today? When breaking down the aspects of heavier-than-air flight, aerodynamic lift has to be generated and this is usually accomplished by wind rushing over a wing. To get us where we are today, early inventors experimented with such contraptions as kites, gliders and airplanes. Without the wind, kites and gliders are rendered useless since their main sustainment of lift is wind. Airplanes on the other hand utilize a means of propulsion to propel them through the air causing wind to generate lift as it rushes over the wings (Bell, 2014).
The history of the general construction of an aircraft and associated components throughout history has been comprised of various materials. Aviation pioneers had to utilize wood as the main component in making their aircraft as they were testing their theories. Heavier-than-air flight was achieved by the Wright Brothers in 1903, when their powered aircraft carried a man aloft and it was only comprised of wood truss structure and thin fabric covered wings. Over the next few years, engine development greatly advanced with more powerful and reliable models that in 1910, Hugo Junkers; a German inventor developed a metal constructed aircraft. This aircraft, called the J-1was constructed with metal trusses and the skin wrapped metal as well. The combination of both a powerful engines and metal construction eliminated the need of stacked wings and a monoplane was developed without the need of wires and wing braces (Federal Aviation Administration, 2012).
By 1926, semi monocoque construction took hold, resulting in stronger and bigger aircraft. The principle behind this construction is instead of having a skeleton structure that the skin was attached and stretched over, only partial structures would be utilized with reinforcing bulkheads and much of the load would be carried with the skin. These reinforced bulkheads would help carry the associated stresses of flight. Using this structure allowed the aircraft to remain light, with powerful engine that eventually lead to the development of plastics (Flannigan, 2010).
Now plastics are not strong enough to support the structure of an entire aircraft that researchers found out but could be used for smaller components and hence, glass fibers was developed to be better known as fiberglass. Owens Corning, in 1935 developed the first fiberglass that when combined with a product such as a plastic polymer could create a lightweight and strong structure. This development is still used today in an industry known as FRP, Fiber Reinforced Polymers (Jones, 2013).
World War II created supply and demand for military aircraft to be lightweight and through further development, Radomes were developed. Radomes are utilized to shelter major electronic components as the structure of the radome is fiberglass and has a transparent quality for radio frequencies. With this breakthrough, the composites industry took a giant leap from scientific research working in laboratories with models and scientific studies, to being full scale production. In 1946 the first composite boat hull was develop and now both the marine and aviation industries benefited from their further research. In the industry today, composites lead the way with the development of carbon fiber, Aramid, Kevlar and graphite composites (Federal Aviation Administration, 2012).
Structural failure contributors Structural failures have been long associated with the individual metal components or complete structures of an aircraft. An aircraft when assembled already has weakness incorporated into them that the manufacture might not associate with. These components will begin to weaken at these points when imposed stresses are acted upon each part during operation. The following are stress prone areas that have the most concentration of structural failures (Bell, 2014):
1. Manufacturer design flaws or machining errors that leave the small imperfections, e.g. holes, burrs, voids, notches and in the forming processes, tight fillet radii.
2. Metal extruded parts might have the same associated flaws during their manufacturer processes that could leave inclusions, pitting, voids etc.
3. From production to service life, corrosion is ever so prevalent that companies pay workers to combat the ongoing spreading of corrosion. Different types of corrosion that cause structural failures are: Uniform attack corrosion, localized corrosion (pitting, crevice, and filiform corrosion), galvanic corrosion, environmental cracking, flow-assisted corrosion, and fretting corrosion.
4. In-flight
What does all that mean?
• Uniform Attack Corrosion: Most common associated form of corrosion that occurs when a chemical reaction to the entire surface of the metal component occurs. The entire exposed surface will corrode to the point of failure. This form does cause the most corrosion of metal components, but it easily overcome since it predictable, preventable and manageable.
• Localized Corrosion: Targets specific metal components in one of three types: pitting, crevice and filiform corrosion.
• Pitting: Pitting is formed by cavities or small holes in the metal that create a galvanic environment making it hard to detect.
• Crevice Corrosion: Just the same as pitting corrosion but with the inhibitor of mirco-environment sitting stagnant. This micro-environment can be found where gaskets, clamps and washers are utilized.
• Filiform Corrosion: Water is the culprit with filiform corrosion. It’s caused when painted or plated surfaces begin to erode and water intrudes behind them.
• Galvanic Corrosion: When two dissimilar metals are mated together with each other to cause a corrosive electrolyte. Of the two metals, each takes a separate roll of anodes and cathodes. To create a galvanic corrosion environment, three conditions must be met:
1. Two dissimilar, electrochemically metals must be present.
2. Metals must be electrically contact as whatever point.
3. An electrolyte must be present and exposed to the metals.
• Environmental Cracking: Environmental conditions against the metals.
• Flow-Assisted Corrosion: Erosion from flight or being susceptible to the environment when rain and wind wear down the outer layers, exposing the metals.
• Fretting Corrosion: Constant repeated wear from the aircraft's weight or vibration from flight. When looking at all of this as a big picture, an investigator during a mishap investigation would be using pretty much any air detective tip to help solve and determine what caused the mishap in the first place.
When a structural mishap occurs, investigators will be looking at all aspects of every piece left of the aircraft. If corrosion was evident, one might suspect the overall maintenance of the aircraft could have been in jeopardy. The SHELL concept could be a great detective tip to utilize because the investigator could compare the Liveware (human) and the factors associated with the aircraft. The accident in general could have been associated with the maintenance malpractice of the maintainers concluding the interface of the pilots not knowing that their aircraft was susceptible to structural failure.
References
Bell, T. (2014, January 14). Types of corrosion: What are the different types of corrosion?. Retrieved
from http://metals.about.com/od/metallurgy/a/Types-Of-Corrosion.htm
Federal Aviation Administration (2012). Aviation maintenance technician handbook. (Vol. 1, pp.
21-75). Oklahoma City, OK: United States Department of Transportation, Federal Aviation
Administration, Airman Testing Standards Branch. Retrieved from http://www.faa.gov
/regulations_policies/handbooks_manuals/aircraft/amt_airframe_handbook/media
/amt_airframe_vol1.pdf
Flannigan, P. (2010, January 19). Semi monocoque, mono-what?. Retrieved from
http://www.aviationchatter.com/2010/01/semi-monocoque-mono-what/
Jones, T. (2013, August 10). Owens corning records , 1938 - present . Retrieved from
http://www.utoledo.edu/library/canaday/findingaids1/MSS-222.pdf
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